The API references for Aquarius and Brizo are auto-generated from the Swagger specs (JSON files) of the live Aquarius and Brizo instances attached to the Nile Testnet. On this site you can’t execute the documented API calls yet. If you need that, you can run a component’s local Swagger UI as outlined in the repository instructions on GitHub.
Additionally, if you need API docs for a past version of Aquarius or Brizo, check out their specs on SwaggerHub: